Amputees in the developing world have few options for replacing lost limbs with effective prostheses. Child amputees are at a special disadvantage because they are still growing and require progressively bigger devices. The University of Toronto’s Matt Ratto and CBM, an international NGO, are using 3-D printers to make precision-fitted plastic sockets that connect a child’s residual limb to standard artificial legs provided by aid agencies. Using the hardware and software designed by Ratto and his team, clinicians in the developing world can 3-D scan a child’s limb and digitally design and print a socket in a few hours.

The resulting custom-fitted device uses about $3 of inexpensive plastic. It requires less than six hours to produce, which means the sockets can be replaced easily and cheaply as the child grows.